Ex Tenebris Venit Lux
by gallifreyedjeans
Summary: MAJOR SPOILERS FOR CoHF! Simon/Isabelle, Post-CoHF. "I think I would've walked this earth ten thousand times over, trying to bring you back to me."


"True love is never lost, not even by a bishop's or a priest's curse, that we cannot regain it, so long as hope has still its bit of green."

- Dante Alighieri, _The Divine Comedy II: Purgatory_

* * *

_Dust, desert, a barren landscape. Sweat drips down the nape of her neck as she lifts her thick, dark hair, a futile effort. Her legs, strong and muscular from years of training, are useless and shaking. She was not meant for this. No Angel was meant to walk through hell._

_Up above, a dark shape shimmers in the heat. If she could only reach it, she could breathe. She believes this in the depths of her soul. So she surges forward, dust filling her lungs, choking her. Stretching out her arms desperately, reaching through the thick and arid air. And then. Her fingernails scrape against something. Something hard as glass – someone._

"_Simon," she gasps, her voice as ragged as the cliffs looming in the distance. "Simon, it's me."_

_Her vision flickers. She can just make out the careless, messy mop of brown hair, dark eyes behind glasses regarding her with a vague disinterest._

"_Who are you?"_

_Dirt and rock rise to meet her, slamming into her knees. _

"_It's me… it's… Isabelle," she chokes out, a final gasp, a ringing in her ears._

_Silence._

* * *

Cool air flooded her lungs and Isabelle gulped it hungrily, sitting bolt upright in her bed. The cotton sheets tangled around her legs were drenched in sweat. Dimly, she registered a mild pain radiating from her right hand, and she glanced down to see little red half-moon marks cut across her palm. Third time this week. At this rate, she'd be permanently scarred. Not like that was something new.

"Izzy?" A blond head poked around her bedroom door, face cast in shadow. "You okay?"

Isabelle wasn't sure she remembered the definition of "okay," so she didn't answer the question. "Is Clary here?"

"What, you assume I'm defiling her in my room, on consecrated ground?" Jace asked in mock horror, stepping fully into the room. "I am a man of virtue, Isabelle Lightwood-"

"A man of virtue who defiled her in a cave in Hell?" Isabelle swung her legs over the side of the bed, pushing her sweaty hair off her forehead.

Jace froze, momentarily caught off guard. "Okay, didn't know you knew about that."

She waved a hand impatiently. "We're girls, Jace. Girls talk."

"Hmm. Strange concept."

"Can you… ask Clary to come here?"

Jace reached into his pocket, pulling out a witchlight stone in one fluid movement. His expression, bathed in pale light, was surprisingly soft. He nodded, then vanished, tossing the witchlight from hand to hand.

The dreams weren't a new thing. They'd been pretty consistent, actually, over the past few weeks. It seemed strange to Isabelle that she had been back at the Institute for so long before the nightmares started – long enough to watch New Year's Eve fireworks explode over the Empire State Building, to watch mounds of snow accumulate in the streets before being reduced to murky slush, to watch crocuses break through the cold, hard earth beneath her feet in Central Park. She supposed she'd been in shock, sleeping deeply and without dreams for months on end.

The Institute was the same as ever, but the people inside it had been changed irrevocably and forever. Alec had collected his things with a feverish excitement and moved to Brooklyn, although of course he still hung around nearly every day. Her mother returned eventually, long dark hair streaked with gray and her expression guarded. Isabelle had not seen her father since the day she departed Alicante.

Though she wouldn't have admitted it, she liked that she could still count on Jace – a newly invigorated Jace, but Jace all the same. He rocketed around the Institute with a ferocity and zest for life that at times amused her and at times made her want to scream. And Magnus and Clary were always around, of course. It tugged at her heart, an echoing sort of ache, when they were all together: Jace gazing lovingly at Clary when he thought she wasn't looking, Alec casually twining his fingers through Magnus's. The five of them were bonded together in some new, strange way – Isabelle sometimes thought that if the parabatai rune could be split five ways, it would encompass the relationship they now shared. The things they had been through… no language had words big enough to explain. And though they were collectively closer than ever, Isabelle felt a longing somewhere deep inside her chest as if something had been torn away from her. She knew she was lucky, that she'd been given the gift of a fresh start. A second chance. But starting over was never as simple as those uninvolved assumed it to be.

The door cracked open for a second time, revealing a small red-haired girl in plaid pajama pants and one of Jace's black t-shirts. Her face, illuminated by what Isabelle assumed was Jace's witchlight stone, wore lines of exhaustion and concern.

"Hey," she said gently, nudging the door shut with her foot. "Jace… Jace said you were yelling in your sleep again."

"Was I?" Isabelle crossed her legs underneath her. She found it difficult to look into the eyes of her friends when she was feeling vulnerable.

"I think it's pretty normal after everything we went through," Clary said as she padded across the room, hopping up onto the foot of the bed.

"Do you dream about it?" Isabelle asked quietly.

"About…?"

"Edom. Walking in that wasteland for hours. Si-" Her voice caught and she clenched her teeth hard, forcing out the name. "Simon."

"Sometimes. Not as much as… other things. When we first got back, I had nightmares about Sebastian… Jonathan…" Clary turned her gaze to the witchlight, flipping it over in her hands several times. "But not so much anymore."

"Do you think you're getting over it? Or coming to terms with it, I guess?"

"I think so. Healing takes time, Izzy. You know that." Clary's voice was soft, kind, and Isabelle wanted to hug her, to cry into her shoulder. Instead, she sat up straighter, pushing the tears down until her throat burned.

"I don't know why the dreams are getting worse," she admitted. "After your mom and Luke's wedding, things were so good… I mean, when Simon showed up like that? And he knew our names? I never thought…"

"I know."

"It's just hard, the in-between time. It's funny… we've seen Hell, or at least something that could be interpreted as Hell…"

"We've seen Hell," Clary affirmed, a dark humor glinting behind her eyes.

"But never anything like Purgatory. I'm starting to feel like this is it."

"Well, maybe." Clary shrugged. "But you know what they say about Purgatory."

"Uh, no."

"You can't stay there forever, right? And you only go on to Heaven. You can only go up, Izzy. You can only go up from here."

Isabelle smiled somewhat shakily, reaching out to fix a tangle in Clary's wild strawberry hair. It was the closest to an affectionate gesture as she could muster.

"You should talk to Simon about all this. Honestly, Iz, don't blame yourself for every bad thing that happens to you."

She flinched - Clary's words stung, but Isabelle knew they held truth.

"I just feel like I'm always walking a tightrope with him now, you know? I never know how much I can say… how much I'm allowed to give away…"

"Well, good thing you've never fallen off a tightrope in your life."

Isabelle offered the other girl a small smile. "I am pretty badass at balancing."

"Oh, the _most _badass."

"I hear you talking about me," Jace called from the hallway, walking past with a toothbrush and tube of toothpaste in hand. Both girls jumped in surprise and laughed.

"Talk to Simon," Clary repeated, her bright green eyes regarding Isabelle with something like love. It was strange, Isabelle thought. She'd never particularly wanted a girl best friend before. But it helped to have someone who was willing to drag your feelings out of the darkness and shine a spotlight on them. The idea of Jace or Alec ever helping her that way was laughable.

"Thanks, Clary. I'll let you get back to whatever unspeakable things you were doing to my brother."

Clary rolled her eyes, but laughed loudly at the same time. It was a happy, free sound that made Isabelle's heart ache for reasons she couldn't quite pin down.

After Clary had left, witchlight in hand, and closed the door gently behind her, Isabelle reached over to grab her cell phone from the windowsill. Aside from a picture of Chairman Meow sitting on Alec's head texted to her by Magnus, she had no new messages. She got the feeling that she and Simon were constantly hovering around each other lately, never knowing which boundaries to cross, the right words slipping like water through their fingers.

With a pang, she remembered lying close to him in the spare bedroom at Magnus's apartment, watching from under dark eyelashes as he told her the entire plot of _Star Wars_. She had pretended to fall asleep after awhile, but he'd kept talking, his voice becoming softer, so she'd stayed awake. The corners of her lips trembled now, a surefire sign ever since she'd been a little girl that she was about to cry. She'd been _vulnerable_, she realized now. Breakable. There was no coming back from that. That was the night she had known she was doomed.

_Simon, _she typed, fingers trembling. _Can we meet somewhere? Maybe tomorrow night?_

Casual, cool, normal. Good. Before she could talk herself out of it, she hit send and placed the phone back on the windowsill. It buzzed the second her head hit the pillow. Abandoning all pretense of coolness, she scrambled back across her bed to read the incoming message.

_Sure. Where?_

* * *

It had rained all day, but by the time Isabelle departed the Institute for Central Park, it had subsided to a light drizzle with slight rumbles of thunder in the distance. She'd loved summer thunderstorms all her life – something about the way they seemed to promise something good appealed to her. 5th Avenue was full of puddles; the pedestrians around her were dodging them carefully, but she splashed along obliviously. She kept trying to smooth her hair back but it was no use in this humidity. _Mental note: get Clary to invent an anti-frizzy hair rune._

Clary had given her a pep talk before she'd left: "DTR. That's all you guys need to do."

"What the hell is-"

"_Define the relationship_," she'd said, clearly fighting the urge to roll her eyes. "Figure out what you guys are to each other now."

"Do I really have to?" Isabelle had responded reluctantly, hovering by the Institute doors and feeling ridiculously uncomfortable. Somehow she had never anticipated receiving relationship advice from Clary.

"I know it's tough – like, it was tough enough for you guys _before _all of this, when you were just 'awkward Daylighter and emotionally-guarded Shadowhunter.' Now you're like… 'newly-mortal former vampire with selective amnesia and even-more-emotionally-guarded Shadowhunter who doesn't even look at other guys anymore because she's so blindly in love."

"That _is_ a mouthful."

Clary had shoved her toward the door. "Go. Talk."

Now, as Isabelle made her way through a wrought-iron gate at the park's northern entrance, the entire situation seemed less funny and more pointless. For a fleeting moment she allowed herself to think of the vision she'd had while entering Edom – for months after they'd returned, she'd blocked it out with the strength of an Iron Sister. Only now was she letting the memory of that imaginary life creep back in like sunlight streaming through cracks in her heart: walking into that apartment, Simon's hand strong and reassuring on her back. A million little things she hadn't even realized she wanted. Her heart's deepest desire.

She shook her head to clear it. It was easy to concentrate now that she was off the busy street, the noise of traffic fading to a distant blur of commotion behind her. The air felt heavier in the park, damp and warm. All she could hear now was the chirping of crickets and the sound of her own boots clicking purposefully along the blacktop road. Then she veered off into the grass and even that noise dimmed into nothing.

He was already here, she realized with a jolt. Up ahead, sitting somewhat nervously on a bench under a sprawling willow tree. He was looking in the complete opposite direction and didn't even turn when a twig snapped under her feet. No more vampire hearing.

"Simon," she called when she couldn't take the silence anymore. He whipped around.

"Oh, hey!" He held up his phone, gesturing to it feebly. "Right on time."

"Yeah, that's me," she said weakly. "An acute sense of punctuality. Move over."

He smiled and scooted over on the bench, making room for her.

"So what's up?"

"I'm really sorry," Isabelle blurted out.

"For what?"

"For… dragging you into all of this." She looked up to meet his eyes, solemn and concerned, and was horrified to hear her own voice quiver. "Clary says we need to define our relationship, but I didn't even ask if you wanted there to be a relationship to define in the first place. I just… those six months without you… I had given up hope that I would ever get you back. And then when the chance came up, I just kind of grabbed it without thinking if maybe you were happier with your life as a mundane."

Simon regarded her for a few minutes, seeming utterly bewildered. For a moment, Isabelle's heart pounded – she was no good at this. Was that too much to lay on him at once? Could he handle it?

He reached out, brushing her hair away from her neck to press one finger gently against the ruby pendant glittering against her chest. She leaned into his touch reflexively.

"You gave me this once," he said slowly. "I remember… you gave it to me and I wore it."

Isabelle gulped, nodding. "Yeah. You said it saved your life."

He looked up abruptly, strands of dark hair falling into his eyes. A warm smile spread across his face.

"Izzy, I know I never fell out of love with you," he said softly. "If you and Magnus hadn't come to find me and helped me remember… I think I would've walked this earth ten thousand times over, trying to bring you back to me."

She leaned back slightly, staring at his face in the semi-dark, stunned into silence. Her hands were shaking.

"I was…" he screwed up his face in concentration, as though he were trying to call up some long-lost dream. "I was always restless when I was awake, and then when I could finally fall asleep, I would just be wandering."

She opened her mouth, then closed it quickly.

"But even before everything happened, Izzy, I think… I remember worrying about losing you," Simon continued. "Whether you died young in battle or as an old woman… I worried about the day when you'd slip away from me. And I'd still be here walking through this damn city, still sixteen… I lost sleep over that."

"You'll never have to walk anywhere alone, idiot," she mumbled, moving in to bury her face into his shoulder. His arms went around her like an impulse he couldn't keep down. "I'm not letting you out of my sight again."

"That sounds good." He leaned back, reaching out to run his fingers along her jawline, tilting her chin up so she had no choice but to look him straight in the eyes. Before their lips met, the reflection of light from the street lamps in his eyes looked like the stars of a galaxy she knew by heart. And then they were kissing, softer and sweeter than ever before. It was like he was trying to relearn her, she thought.

Would it ever be like it was before? Maybe not, but it could be new. That was the thing, she realized as his hands twined through her hair, carefully pulling her closer – you could never undo the damage of a broken heart, but you could fill the broken pieces with light to shine through the cracks.

They broke apart and Isabelle leaned her forehead against his, trying to catch her breath.

"So we're supposed to define the relationship, huh?" Simon whispered, laughing.

"That's what your meddler of a best friend says."

"Okay. Marry me."

Isabelle jerked back, heart stuttering in her chest. "What?!"

"Not like, right _now_." Simon grinned sheepishly. "Just… someday. When I'm a Shadowhunter… when I've been a Shadowhunter for awhile, when I can really feel what it means. When we're ready. I want to marry you."

The chorus of cricket chirping seemed to rise in a crescendo with every minute that Isabelle remained silent. Simon's smile faltered, an unnatural-looking flush creeping high across his cheekbones, but he did not look away. For the third time, the words burst from his lips: "Isabelle Lightwood. Will you marry me someday?"

Something strange was happening. Isabelle had cried before, obviously, but never like this; it was like a dam had broken inside her. Her eyes fluttered shut and she saw several bright images flash behind her eyelids: her mother bending over her bed, kissing her goodnight; eleven-year-old Jace and Alec fighting clumsily in the weapons room, laughing loudly; a wide-eyed baby Max clapping with delight; the craggy ceiling of a cave flickering feebly before her eyes and Simon's cold as stone body curling close to her, holding her until she fell asleep. Little moments, little memories, tremendous emotions she had shoved inside until there was no room to ever let them see sunlight.

"_Yes_," she said in a voice like a strangled sob, her face hot and wet with tears.

Laughing, he pulled her down onto him, their arms and legs colliding painfully. His breath was warm on her cheek, his heartbeat steady against her chest. Alive. He was so alive. Together, they were so alive.

* * *

**Soooo this is the result of my rush of emotions after CoHF, as you can probably tell. This is just intended to be a one-shot, and in case you're wondering, I'm not abandoning Antebellum! I just wanted to take a bit of a break because a) real life has been crazy and b) I was wary of writing something that would immediately be discredited by CoHF. I don't want to make any concrete promises, but I fully intend to update it as soon as I possibly can. **

**Anyway, thanks for reading! xx**


End file.
